1. Technical Field
Exemplary embodiments relate to semiconductor devices, and more particularly to a voltage-controlled oscillator and a phase-locked loop circuit which may include the voltage-controlled oscillator.
2. Description of the Related Art
Phase-locked loop (PLL) circuits are commonly included in semiconductor memory devices for generating clock signals. A PLL circuit typically includes a voltage-controlled oscillator (VCO). The VCO may generate an oscillating signal having a desired frequency in response to a voltage control signal. When the voltage control signal changes linearly, the frequency of the oscillating signal also changes linearly. Semiconductor memory devices now use lower power supply voltages. Accordingly, to accommodate the lower power supply voltage, the current consumption in the VCO must be reduced.